Imaging applications such as those involving cameras, video cameras, microscopes and telescopes have been highly susceptible to image error conditions including those relating to aberrations. Generally, aberrations are imperfections in the optical formula of a lens that prevent perfect convergence. Such aberrations may include, for example, spherical aberration, chromatic aberration, distortion, curvature of the light field, oblique astigmatism and coma. A classical case involves spherical aberration due to rays refracting through a plano-convex lens. This lens has one flat side and one convex spherical side, with rays passing through the periphery of the spherical interface refracting too strongly and converging at a depth closer to the lens, relative to rays that pass close to the center of the lens. Due to this strong refraction, the light from a desired point is blurred over a spot on the image plane, thereby reducing contrast and resolution. Such issues have motivated intense study of image correction and optimization over the years, including contributions from such names as Gauss, Galileo, Kepler, Newton, and innumerable others.
Correction for aberrations has often involved the use of multiple optical elements, which tend to add bulk, expense and weight to imaging devices. In some applications benefiting from small-scale optics, such as camera phones and security cameras, the physical limitations associated with the applications make it undesirable to include additional optics. Moreover, for many digital imaging applications, as the number of photosensors used to collect image data increases and as the arrangement and processing of data from the same becomes increasingly important, aberration and other conditions that raise issue with the creation of images can significantly hinder the ability to create accurate images.
The process of correcting aberrations by combining glass elements has been carried to remarkable extremes. Zoom lenses provide perhaps the most dramatic illustration of this phenomenon. Zooming a lens requires a non-linear shift of at least three groups of lens elements relative to one another, making it very challenging to maintain a reasonable level of aberration correction over the zoom range. To address these challenges, extremely sophisticated and complex design forms have evolved and are now commercially available. As an example, commodity 35 mm zoom lenses generally contain no fewer than 10 different glass elements, and some have as many as 23. Most if not all modern lens design work is computer-aided, where design forms are iteratively optimized by a computer. A large numbers of lens elements provide greater degrees of freedom for such a computer to achieve the desired optical quality. These approaches add bulk, expense and weight to these lenses.
Difficulties associated with the above have presented challenges to imaging applications, including those involving the acquisition and altering of digital images.